I wanna steampunk society. Eco friendly and uber cool.

[Subduction Zone]

But you can't use most of these as viable working fluids in a heat engine, can you? Has anyone built a sodium vapour engine? A helium engine?

I assume by a steam engine you mean water/steam is the working fluid. You can certainly superheat the steam, to supercritical temperatures if you want, though the pressures will necessitate a lot of heavy metal. That gives you a T1 of 600C or so. T2 will also need to be high enough to get an acceptable rate of heat rejection from the radiator, as @Subduction Zone points out.

Has anyone done the sums on all this?

Not at five in the morning when I should be sleeping. But black body radiation is relatively easy to calculate. What one needs would be the temperature at the radiation end and how much energy it needs to get rid of. Would a 50% efficiency be a good place to start? Let's say that mirrors are involved that raise the input temperature. One cannot get anywhere near Sun temperatures since we cannot melt our conduits.

 

[exchemist]

You misunderstood. Yes, the Sun is about 6,000 K, at the surface. The temperature of its radiation by the time it gets to Earth is far less. Mirrors can concentrate some of that heat, but radiating it is going to be an engineering nightmare.

That's not my understanding. The "temperature" of the radiation is determined by its spectral distribution (its "black body", or quasi-black body spectrum), not by intensity, so far as I am aware. Thermodynamically, the temperature of the suns surface is, I think, in theory available from solar radiation.

 

[Revoltingest]

I'll start with a car.

What else should we add?

He said: "the technology was well before its time"
He should've said: "the technology was well after its time"

 

[Subduction Zone]

That's not my understanding. The "temperature" of the radiation is determined by its spectral distribution (its "black body", or quasi-black body spectrum), not by intensity, so far as I am aware. Thermodynamically, the temperature of the suns surface is, I think, in theory available from solar radiation.

Temperature is just do to the amount of heat energy that a group of molecules have, so if you could concentrate the light of the Sun so that it was more intense than at the surface the temperature one could attain would be even higher. I was in bed and being very loose in my terminology. For a perfect black body at Earth's position the temperature would be about 0 C in fact it would be:

"An ideal thermally conductive blackbody at the same distance from the Sun as Earth would have a temperature of about 5.3 °C (41.5 °F). However, because Earth reflects about 30%[17][18] of the incoming sunlight, this idealized planet's effective temperature (the temperature of a blackbody that would emit the same amount of radiation) would be about −18 °C (0 °F).[19][20] The surface temperature of this hypothetical planet is 33 °C (59 °F) below Earth's actual surface temperature of approximately 14 °C (57 °F).[21] The greenhouse effect is the contribution of greenhouse gases to this difference"

Greenhouse effect - Wikipedia

Black body radiation has been understood since the 1800's. The Earth is warmer than a perfect black body and even warmer still than a body with Earth's albedo "should" have. The clear excess temperature of the Earth is what led to the Greenhouse effect. Okay far enough off of topic.

One could concentrate the energy but only to a point. If one uses molten sodium rather than water one would still have the limitation of not being able to harvest more energy than the metal conduits of the molten sodium could handle. Still it would be interesting to get some proposed figures. What I worry about is trying to radiate off heat after it has been harvested.

 

[Heyo]

Temperature is just do to the amount of heat energy that a group of molecules have, so if you could concentrate the light of the Sun so that it was more intense than at the surface the temperature one could attain would be even higher. I was in bed and being very loose in my terminology. For a perfect black body at Earth's position the temperature would be about 0 C in fact it would be:

"An ideal thermally conductive blackbody at the same distance from the Sun as Earth would have a temperature of about 5.3 °C (41.5 °F). However, because Earth reflects about 30%[17][18] of the incoming sunlight, this idealized planet's effective temperature (the temperature of a blackbody that would emit the same amount of radiation) would be about −18 °C (0 °F).[19][20] The surface temperature of this hypothetical planet is 33 °C (59 °F) below Earth's actual surface temperature of approximately 14 °C (57 °F).[21] The greenhouse effect is the contribution of greenhouse gases to this difference"

Greenhouse effect - Wikipedia

Black body radiation has been understood since the 1800's. The Earth is warmer than a perfect black body and even warmer still than a body with Earth's albedo "should" have. The clear excess temperature of the Earth is what led to the Greenhouse effect. Okay far enough off of topic.

One could concentrate the energy but only to a point. If one uses molten sodium rather than water one would still have the limitation of not being able to harvest more energy than the metal conduits of the molten sodium could handle. Still it would be interesting to get some proposed figures. What I worry about is trying to radiate off heat after it has been harvested.

I did look up the Boltzmann law and, after eliminating the nitty-gritty it comes down to E = AσT⁴. (σ being the Boltzmann constant 5.6*10⁻⁸, A = area and T temperature in K).
At about 85° C (a reasonable temperature for a water heated radiator) we can radiate off about 1 KW of excess heat per m². (And I think we agree that getting rid of the heat is the limiting factor.)
I also looked up the energy production on the ISS. Their solar panels produce about 70 W per m².

 

[Subduction Zone]

I did look up the Boltzmann law and, after eliminating the nitty-gritty it comes down to E = AσT⁴. (σ being the Boltzmann constant 5.6*10⁻⁸, A = area and T temperature in K).
At about 85° C (a reasonable temperature for a water heated radiator) we can radiate off about 1 KW of excess heat per m². (And I think we agree that getting rid of the heat is the limiting factor.)
I also looked up the energy production on the ISS. Their solar panels produce about 70 W per m².

I looked up the ISS to see how they stay cool. I know that space is treated as if it were cold but any body that generates internal heat will tend to warm if some method is not found to get rid of the heat generated by human bodies and electronics:

Inside the ISS, there are a lot of electronic devices that generate heat. The astronauts themselves also generate heat. A system called the Active Thermal Control System (ATCS) keeps the temperature inside the ISS comfortable for the astronauts. The ATCS has three subsystems: one for heat collection, one for heat transportation, and one for heat rejection.

Heat collection happens through several heat exchangers around the ISS. These keep the temperature at around 24 °C, allowing astronauts to work comfortably in t-shirts.

Heat transportation is done using closed loops of pipes filled with water. The heat exchangers heat up the water in the pipes, which then transport the heat to another set of closed loops of pipes filled with ammonia, which freezes at a much lower temperature (-77 °C) than water.

The pipes filled with ammonia transport the heat outside the ISS to the Heat Rejection Subsystem (HRS) radiators. These radiate (transfer) excess heat into space. The HRS radiators are the two big sets of light-coloured panels that can be seen on the outside of the ISS near the crew modules.

Temperature on Earth and on the ISS

Nothing technical there. I might keep looking to see at what rate they can dump excessive heat.

 

[Heyo]

Nothing technical there. I might keep looking to see at what rate they can dump excessive heat.

Black-body radiation - Wikipedia

There are several factors but the main ones are area and temperature⁴. (Assuming you can turn your radiator to face space and you have painted it to be as perfectly black as you can.) As radiation goes up with the forth power of temperature, you may want to pump up the heat of your exhaust pipe.

 

[Subduction Zone]

Black-body radiation - Wikipedia

There are several factors but the main ones are area and temperature⁴. (Assuming you can turn your radiator to face space and you have painted it to be as perfectly black as you can.) As radiation goes up with the forth power of temperature, you may want to pump up the heat of your exhaust pipe.

I am not sure about painting it black. If you study black body radiation you will see that there is an albedo correction too. Objects with higher albedos are cooler than a perfect black body. And "black" for us only applies to visible shades of light. The radiator itself would not get anywhere near the "temperature of light". In other words if it were black it would be apt to absorb solar radiation, perhaps largely making it ineffective. If it were as close to white in the visible spectrum as possible and yet dark in the infrared would be better to me. And in that article it did point out that the radiators were "light colored" oops excuse me, "light coloured". In other words they are designed to reflect as much high energy visible light as possible without affecting radiation at lower frequencies.

 

[Heyo]

I am not sure about painting it black. If you study black body radiation you will see that there is an albedo correction too. Objects with higher albedos are cooler than a perfect black body. And "black" for us only applies to visible shades of light. The radiator itself would not get anywhere near the "temperature of light". In other words if it were black it would be apt to absorb solar radiation, perhaps largely making it ineffective. If it were as close to white in the visible spectrum as possible and yet dark in the infrared would be better to me. And in that article it did point out that the radiators were "light colored" oops excuse me, "light coloured". In other words they are designed to reflect as much high energy visible light as possible without affecting radiation at lower frequencies.

I assumed you could turn your radiator to face deep space so that incoming radiation can be neglected. But you are right in that you want them to be "black" for the colour of light you are emitting.

 

[Subduction Zone]

I assumed you could turn your radiator to face deep space so that incoming radiation can be neglected. But you are right in that you want them to be "black" for the colour of light you are emitting.

That can be a bit difficult when an object is in orbit around a planet. But otherwise it seems feasible.

 

[Heyo]

That can be a bit difficult when an object is in orbit around a planet. But otherwise it seems feasible.

Yes, the ISS is more like a high flying plane than an object in low orbit. Earth appears under an angel of 140° filling a big chunk of the visible field and not being an ideal radiation sink.

 

[exchemist]

Temperature is just do to the amount of heat energy that a group of molecules have, so if you could concentrate the light of the Sun so that it was more intense than at the surface the temperature one could attain would be even higher. I was in bed and being very loose in my terminology. For a perfect black body at Earth's position the temperature would be about 0 C in fact it would be:

"An ideal thermally conductive blackbody at the same distance from the Sun as Earth would have a temperature of about 5.3 °C (41.5 °F). However, because Earth reflects about 30%[17][18] of the incoming sunlight, this idealized planet's effective temperature (the temperature of a blackbody that would emit the same amount of radiation) would be about −18 °C (0 °F).[19][20] The surface temperature of this hypothetical planet is 33 °C (59 °F) below Earth's actual surface temperature of approximately 14 °C (57 °F).[21] The greenhouse effect is the contribution of greenhouse gases to this difference"

Greenhouse effect - Wikipedia

Black body radiation has been understood since the 1800's. The Earth is warmer than a perfect black body and even warmer still than a body with Earth's albedo "should" have. The clear excess temperature of the Earth is what led to the Greenhouse effect. Okay far enough off of topic.

One could concentrate the energy but only to a point. If one uses molten sodium rather than water one would still have the limitation of not being able to harvest more energy than the metal conduits of the molten sodium could handle. Still it would be interesting to get some proposed figures. What I worry about is trying to radiate off heat after it has been harvested.

That's very interesting about the greenhouse effect on Earth, certainly. However I don't think it describes what we would be talking about. If, instead of a perfectly conductive (spherical?) black body, you had a perfectly black insulated plate with a perfectly silvered back, so that it could only lose heat by radiation from the front surface, it would only exchange radiation with the surface of the sun and would, I believe, reach thermal equilibrium at the same temperature.

OK, in practice we would be taking heat out of course, to boil water, so the temperature of the heater would be a lot lower, but it is not true to imagine that the temperature would be limited to 5.3C.

 

[Subduction Zone]

That's very interesting about the greenhouse effect on Earth, certainly. However I don't think it describes what we would be talking about. If, instead of a perfectly conductive (spherical?) black body, you had a perfectly black insulated plate with a perfectly silvered back, so that it could only lose heat by radiation from the front surface, it would only exchange radiation with the surface of the sun and would, I believe, reach thermal equilibrium at the same temperature.

OK, in practice we would be taking heat out of course, to boil water, so the temperature of the heater would be a lot lower, but it is not true to imagine that the temperature would be limited to 5.3C.

I know, it does not work the same way at all. It was just an aside, something else besides just radiative cooling was known to be going on because the Earth was too warm.

But getting to your example. The perfectly black front plate would both absorb and radiate heat. And the rate that it radiates at is given by the Stefan Boltzmann Law. That rate is only based on the object's temperature. When its rate of radiation matches the rate of incoming energy its temperature will stabilize. As you know the energy per square meter from the Sun drops off following the inverse square law. Which only makes sense since the area that the energy passes through increases with the square of the distance. At this distance even your object has would not get anywhere close to the Sun's temperature.